The periderm is a protective layer of tissue that develops in woody plants. It replaces the epidermis as the outermost cell layer of the stem and root. The periderm consists of three layers:

- The cork cambium, or phellogen, is a thin layer of meristematic cells that produces cork cells to the outside and phelloderm cells to the inside. Cork cells are dead at maturity and their cell walls contain suberin, a waxy substance that helps to waterproof the plant.

- The cork, or phellem, is the outermost layer of the periderm and consists of several layers of dead cork cells.

- The phelloderm is the innermost layer of the periderm and consists of several layers of living parenchyma cells.

The periderm provides protection against desiccation, temperature extremes, and pathogens. It also helps to store food and water and transport nutrients.